This article by Will Evans, Director, Experience Design for Semantic Foundry is quite insightful on the importance of sketching as part of the design process.
“In designing mostly interactive systems (spaces, processes, and artifacts for people to use), I must increasingly stretch the limits of communication tools to explore and document what it will be like to interact with the things I create. Artifacts used in communicating design create an inherent frame of experience between the subjective response of the person for whom I design, and my expectations of their response. There is a divergence of meaning in that the audience can only experience the communications artifact, not the object being communicated.” – Will Evans
Read the full article here: Shades of Grey: Thoughts on Sketching | UX Magazine.